1. Field of the Invention
The present invention relates to a method for manufacturing a sheet molded body made from a decorated sheet having a design, and a method for manufacturing an insert molded body which includes a resin molded body integrated with the sheet molded body.
2. Background Art
An insert molded body in which a decorated sheet having a pattern or the like integrated into the surface of a resin molded body has been widely used in interior or exterior parts of automobiles, for example.
As an example of methods for manufacturing the insert molded body, the following method is disclosed in Japanese Laid-Open Patent Application No. 2001-225350.
In the above-mentioned method, a decorated sheet which is heated and softened is firstly absorbed by vacuum suction onto the surface of a vacuum molding male die so that it closely contacts the surface and is three dimensionally formed into a shape corresponding to the surface of the male die. Then, the three dimensionally formed decorated sheet is placed in an injection molding female die. After this, the injection molding dies are mold closed, and a melted resin is introduced into the cavity. In this manner, an insert molded body, which includes the decorated sheet and a resin molded body integrally formed with the back surface side of the decorated sheet, is obtained.
However, in the process of three dimensionally forming the decorated sheet in the above-mentioned method, air tends to remain between the vacuum molding male die and the decorated sheet, and there are cases that the vacuum molding male die does not closely contact the decorated sheet. If the decorated sheet is three dimensionally formed while there is no close contact with the vacuum molding male die, there is a danger that a crease is generated on the decorated sheet after molding or the desired shape of the decorated sheet cannot be obtained. As a result, problems may also be caused for an insert molded body which uses the decorated sheet, such as poor contact between the decorated sheet and the resin molded body, or a deterioration in appearance.
Also, in the method described in Japanese Laid-Open Patent Application No. 2001-225350, since the heated and softened decorated sheet is vacuum absorbed onto the surface of a vacuum molding male die without expanding the decorated sheet, a portion of the decorated sheet which closely contacts the surface of the male die by vacuum suction does not expand significantly and only the portions that contact the surrounding surfaces of the male die rapidly expand during the vacuum molding. Accordingly, since the degree of expansion of the decorated sheet thus obtained differs from portion to portion, the pattern thereof sometimes appears to be different depending on the portion, and the quality of the design is compromised. Also, since the thickness of the portion which contacts the surrounding surfaces of the male die becomes extremely thin, a crease may be generated in that portion or poor contact with a resin molded body may be induced during an insertion molding, and defective products tend to be produced.